1. Markarian 421 with MAGIC telescope Daniel Mazin for the MAGIC Collaboration Max-Planck-Institut für Physik, München mazin@mppmu.mpg.de

2. Outline The MAGIC telescope AGN Markarian 421 Data sample Analysis status Conclusion / outlook

3. The MAGIC Telescope The largest imaging atmospheric Cherenkov Telescope with 236 m 2 mirror surface 3.5° FoV Camera with 576 high-QE PMT’s Design optimized for: Low energy threshold E  = 30 GeV Fast repositioning t p < 30 sec Canarian Island La Palma, 2200 m asl

4. AGN Markarian 421 Right Ascension 11:04:27 (h:m:s) Declination: +38:12:32 (deg:m:s) BL Lac object, z=0.030 (370 MLy) Mass: 1.9 10 8 M  First detected extragalactic TeV  -ray source (Punch et al, 1992) Many known flares, active in 2004 Well described by SSC models (e.g. Konopelko et al, ApJ,597:851) Still many correlations not understood Aimo Sillanpaa, NOT

5. Advantages of simultaneous observations One experiment: one decade in energy Two experiments: two decades Multiwavelength campaigns Correlation studies Change hardness during flares (Krennrich et al, ICRC 2003) Light curves, look for fast flares HEGRA, A&A,393,89 HEGRA, A&A,410,813 + X-calibration of the instruments

6. MAGIC data sample DatecommentsPreliminary results (sky plot of number of excess events): February 2004 flare, commissioning phase April 2004 Strong flare, Overlap with HESS, commissioning phase December 2004 Overlap with HESS This talk Sky plot:

7. MAGIC data sample (December 04) Triggered by RXTE and VERITAS (Dec 14) After a few hours: MAGIC and HESS agreed to make simultaneous observations Due to bad weather only 2 days of MAGIC data: 18 and 19 December DateObs.timeMean zenith angle (deg) comments 18 Dec55 min4830 min with HESS 18 Dec59 min12.5 19 Dec30 min5130 min with HESS 19 Dec79 min21

8. Comparison of MC predictions and data Good agreement between mc-gamma and excess events

9. Estimate of energy resolution SIZE (total number of PEs) simplest energy estimator improve energy estimation including other image parameters optimized estimator using Random Forest technique 20% (30%) @ 1 TeV (100 GeV) Log 10 (E est [GeV]) (E est -E true )/E true Sigma[%] Log 10 (E true [GeV])

10. Mrk 421: False source plot For the whole data sample (3.7h): After cuts: over 700 excess events Point-like source ( < 0.15 deg ) 11.07 38.19 11.10 11.1411.04 11.00 38.69 39.19 37.69 Dec (deg) RA (h) Number of excess events

11. Alpha plots For the 4 samples: Clear signal detection in all of them Energy range for this analysis: high zenith angle: 250 GeV – 2 TeV low zenith angle: 100 GeV – 1 TeV 18/12/05, =4818/12/05, =12 19/12/05, =51 19/12/05, =21

12. Light curve (X-ray) 17-20 December 2004 X-rays: no significant variation Optical data (KVA): quiescent state 18/12 19/12 Dec 04 Apr 04

13. Light curve (GeV, MAGIC) Low zenith angle points only, 20 min bins No strong variations visible Looks like we just missed the peak of the flare (weather!) Soon to come: Energy spectrum and full light curve for the MAGIC data Combined MAGIC – HESS data analysis 40044005(mjd-49353)

14. Conclusions / Outlook Coordinated ground based Cherenkov telescopes observations going on Almost full time coverage possible (CANGAROO, HESS, VERITAS, MAGIC) Up to 3 decades in energy due to energy threshold and different zenith angle conditions MAGIC clearly detected a flare of Markarian 421 in December 2004 Due to bad weather: too late for the peak of the flare 3.7 hours of data: enough statistics to produce light curves and energy spectra  work in progress

15. Thank you